main.c

#include <unistd.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>

#define CONSUMER_ERROR(msg)			\
    do {perror("Consumer Error: " msg "\n"); exit(1); }while(0)

#define PRODUCER_ERROR(msg)			\
    do {perror("Producer Error: " msg "\n"); exit(1); }while(0)

#define PRODUCER_PRINT(format, ...) printf ("<<Producer>> (pid: %d): " format "\n", getpid(), ##__VA_ARGS__ )
#define CONSUMER_PRINT(format, ...) printf ("<<Consumer>> (pid: %d): " format "\n", getpid(), ##__VA_ARGS__ )

#define SHM_NAME "/my_sharedmem"

#define STACK_SIZE 1000

void producer();
void consumer();
int fd_err_handle(int);

int main(int argc, char *argv[])
{
    pid_t pID = fork();
    if (pID == 0) {
	// Code only executed by child process
	printf ("Child is born\n");
	consumer();

    } else if (pID < 0) {
	perror("Unable to fork\n");
	exit(1);
    } else {
	// Code only executed by parent process
	printf ("Parent surivived\n");
	producer();
    }
    return 0;
}


void producer()
{
    int fd, d;
    unsigned* spool, optimizable1;

    PRODUCER_PRINT("started");
    fd = shm_open(SHM_NAME, O_CREAT | O_RDWR, S_IRWXU | S_IRWXG | S_IRWXO);
    if (fd<0) {
	PRODUCER_ERROR("Failed to open shared memory.");
	exit(1);
    }

    ftruncate(fd, sizeof(unsigned));

    PRODUCER_PRINT("memory file opened");

    spool = mmap(NULL, sizeof(unsigned), PROT_WRITE|PROT_EXEC, MAP_SHARED, fd, 0);
    PRODUCER_PRINT("mmaped to %p", spool);
    perror("<<Producer>>");


    /* Write and flush to the pool. */
    for (d=0; d<STACK_SIZE; d++) {
	*spool = d;
	msync(spool, sizeof(unsigned), MS_SYNC | MS_INVALIDATE);
    }

    PRODUCER_PRINT("ended");
}

void consumer()
{
    unsigned* spool;
    int fd, read, tmp, d, top = 0;
    unsigned stack[STACK_SIZE];

    CONSUMER_PRINT("started");
    fd = shm_open(SHM_NAME, O_RDONLY, 0);

    if (fd < 0) {
	CONSUMER_ERROR("Failed to open shared memory.");
	exit(1);
    }
    CONSUMER_PRINT("memory file opened");
    spool = mmap(NULL, sizeof(unsigned), PROT_READ, MAP_SHARED, fd, 0);
    perror("<<Consumer>>");

    CONSUMER_PRINT("mmaped to %p", spool);

    /* Read the pool many many times. */
    for (d=0; d<STACK_SIZE; d++) {
	tmp = *spool;
	stack[top] = tmp;
	read = tmp;
	top = (top+1);
    }
    CONSUMER_PRINT( "Distinct numbers tracked: %d", top);
    for (d=0; d<top; d++) {
	printf("\t%d\n", stack[d]);
    }
    CONSUMER_PRINT("ended");
}